Earth Resources.pdf

EARTH’S RESOURCES NONRENEWABLE RESOURCES A nonrenewable resource is a natural resource that cannot be re-made or re-grown at a scale comparable to its consumption.  RENEWABLE RESOURCES Renewable resources are natural resources that can be replenished in a short period of time. S...

EARTH’S RESOURCES NONRENEWABLE RESOURCES A nonrenewable resource is a natural resource that cannot be re-made or re-grown at a scale comparable to its consumption.  RENEWABLE RESOURCES Renewable resources are natural resources that can be replenished in a short period of time. Solar Geothermal Wind Biomass Water  The Water Cycle (moves through the atmosphere, biosphere, hydrosphere & lithosphere) In the Water Cycle, water passes from vapor in the atmosphere as rain onto the land or body of water The water then transfers from the lithosphere back into the atmosphere through evaporation (liquid water changes to water vapor) & transpiration (liquid water from plants changes to water vapor). That water then condenses (water vapor changes to liquid water) in the colder atmosphere and it starts to rain, moving water from the atmosphere to the hydrosphere continuing the cycle again. (Images from http://ga.water.usgs.gov/edu/graphics/watercyclesummary.jpg and http://dnr.wi.gov/org/caer/ce/eek/earth/groundwater/watercycle.htm)  The Nitrogen Cycle (moves through the atmosphere, biosphere & lithosphere) Nitrogen makes up 78% of Earth’s atmosphere. Most nitrogen is in gaseous form, which makes it not usable by life on Earth. Microbes (microscopic organisms) in the soil and in roots of some plants convert or “fix” nitrogen into a form that plants can use (nitrogen fixation) Humans and animals get the nitrogen compounds by eating plants or by eating other animals that have eaten the plants. Microbes return the nitrogen from decaying matter and waste to the gaseous form and the cycle continues (Image from http://www.kidsgeo.com/geography-for-kids/0161-the-nitrogen-cycle.php and http://www.h2ou.com/h2nitrogencycle.htm)  The Oxygen Cycle (moves through the atmosphere, biosphere, hydrosphere & lithosphere) Oxygen can be dissolved in the air or in water. Plants and animals breathe oxygen and return it to the air and water as carbon dioxide. Through photosynthesis, plants convert carbon dioxide and water into carbohydrates, and release oxygen. Algae in the oceans and other water bodies replace about 90% of all oxygen used on our planet. (Images from http://www.copperwiki.org/index.php?title=File:Oxygen_Cycle.jpg and http://www.exploringnature.org/db/detail.php?dbID=27&detID=1186)  The Carbon Cycle (moves through the atmosphere, biosphere, hydrosphere & lithosphere) Photosynthesis and respiration. Plants and animals breathe oxygen and return it to the air and water as carbon dioxide. Large amounts of carbon are stored in the form of Fossil fuel (oil, coal, natural gas). Burning fossil fuels releases carbon into the atmosphere in the form of Carbon Dioxide (CO2) Large amounts of carbon are also stored in tissues of trees (such as wood). So, carbon Dioxide (CO2) is also released when wood is burned or when it decays. Carbon Cycle Carbon in our Earth  The Energy Cycle The movement of Energy into and out of the Earth System A.K.A. The Energy Budget Balance is the Key: equal energy in and out  Solar Energy 99.985% of total energy ØIt comes from nuclear reactions in the sun Drives winds, ocean currents, waves, and weather.  Geothermal Energy Geo means Earth Thermal means Heat 0.013% Drives the movement of Earth’s crust, Volcanoes, Earthquakes, and Geysers Important role in the Rock Cycle  Tidal Energy 0.002% of the energy budget Results from the moon’s pull on the Earth’s oceans Powerful enough to slow down the Earth  Main Concept: Minerals are the building What is a mineral? blocks of rocks! There are five main criteria for something to be a mineral: a) It must be solid a) It must occur naturally (not man-made) b) It is made of non-living material (never alive) c) It has a definite chemical formula (NaCl=salt) d) It has a crystal structure (Precious?) Soil, Rocks, and Minerals are Natural Resources Soil is the loose top layer of the earth’s surface. All soil comes from rocks and minerals. A rock is a natural solid made of one or more minerals. Minerals are natural solids usually formed as crystals that are found in rocks. All rocks are made of one or more minerals. Where do minerals come from? § Mineral crystals can form in two main ways: From stuff dissolved in liquids From Cooling (Evaporation & Hot Water) molten material  Minerals & Crystals from Magma & Lava “Extrusive” Cooling: Lava cools Fast (Short Time = Small Crystals) Minerals form from hot magma as it cools inside the crust, or as lava cools on the surface. When these liquids cool to a solid, they form crystals (minerals). Size of the crystal depends on time it takes to freeze into a solid. “Intrusive” Cooling: Magma cools slowly (Long Time = Large Crystals) Minerals Crystal Size When the hot material cools fast, it has smaller crystal size. When it cools slowly, it has large crystals. Granite Rhyolite You can see individual crystals You can’t see many in Granite individual crystals in Rhyolite = cooled slowly = cooled very fast Minerals formed by Evaporation § Some minerals form when solutions/mixtures evaporate: § When water evaporates, it leaves behind the stuff that’s dissolved in it. § The longer it takes to evaporate, the larger the crystal. § i.e. salt & water – ocean, § Halite, Gypsum, Calcite. ***All the white stuff = salt mineral crystals that formed when the water of this lake evaporated. The mineral material was left behind These salt crystals formed from salt water because as the water evaporated, the salt wasn’t dissolved anymore. So the chemical energy in salt takes over and crystals form. Do you notice the characteristic cubic crystalline shapes? Polymorphs Minerals with the same composition, but different crystal structure. Common Rock-Forming Minerals Minerals fall into a small number of related “families” based mainly on the anion in them Silicates Most abundant minerals in the Earth's crust Silicate ion (tetrahedron), SiO44- n Quartz (SiO2), K-feldspar (KAlSi3O8), olivine ((Mg, Fe)2SiO4), kaolinite (Al2Si2O5(OH)4) Quartz (SiO2) Silicate structure Most of the most common rocks in the crust are silicates Silicate tetrahedra can combine in several ways to form many common minerals Typical cations: K+, Ca+, Na+, Mg2+, Al3+, Fe2+ Different numbers of oxygen ions are shared among tetrahedra Carbonates Cations with carbonate ion (CO32-) Calcite (CaCO3), dolomite (CaMg(CO3)2), siderite (FeCO3), smithsonite (ZnCO3) Make up many common rocks including limestone and marble Calcite (CaCO3) CaCO3 + 2H+ = Ca2+ + CO2 + H2O Smithsonite (ZnCO3) Oxides Compounds of metallic cations and oxygen Important for many metal ores needed to make things (e.g., iron, chromium, titanium) Ores are economically useful (i.e., possible to mine) mineral deposits Hematite (Fe2O3) Sulfides Metallic cations with sulfide (S2-) ion Important for ores of copper, zinc, nickel, lead, iron Pyrite (FeS2), galena (PbS) Galena (PbS) Sulfates Minerals with sulfate ion (SO42-) Gypsum (CaSO4.H2O), anhydrite (CaSO4) Gypsum  Gypsum Cave of the Crystals 1,000 feet depth in the silver and lead Naica Mine 150 degrees, with 100 % humidity 4-ft diameter columns 50 ft length Identification of Minerals Chemical composition (microprobes and wet chemical methods) Crystal structure (X-ray diffraction) Physical properties Physical properties Hardness Physical properties Hardness Cleavage: tendency of minerals to break along flat planar surfaces into geometries that are determined by their crystal structure Cleavage in mica Cleavage in calcite Halite (NaCl) Physical properties Hardness Cleavage Fracture: tendency to break along other surfaces (not cleavage planes) Conchoidal fractures Physical properties Hardness Cleavage Fracture Luster (metallic, vitreous, resinous, earthy, etc.) Color (often a poor indicator; streak color is better) Specific gravity Crystal habit (shape) How do we identify Minerals? We use the different physical and chemical properties of the mineral to identify it from other different minerals Luster: Describes how light is reflected from a minerals surface. Streak: Is the color of the minerals powder when dragged across a surface. Crystal shape: Different minerals make different crystal shapes Hardness: Hardness is determined by a “scratch test”. Color: Every mineral has some natural color…ex: Gold, Blue, Clear… Etc: There are many other types of properties we use but these are the big ones Special Properties Some minerals display strange properties. These can include: Magnetism, fluorescence, and reactivity. Fizzing! The particles of minerals These minerals glow The minerals in of this rock act like magnets in the dark. this rock react A black light really brings it out! with acid  Mineral Resources Building Metallic Minerals Stone, Sand, Gravel, Limestone Non-ferrous: Copper, Zinc, Tin, Non-metallic Minerals Lead, Aluminum, Titanium, Manganese, Magnesium, Mercury, Sulfur, Gypsum, Coal, Barite, Salt, Vanadium, Molybdenum, Clay, Feldspar, Gem Minerals, Tungsten, Silver, Gold, Platinum, Abrasives, Borax, Lime, Magnesia, Rare Earths Potash, Phosphates, Silica, Fluorite, Asbestos, Mica, Lithium Energy Resources Metallic Minerals Fossil Fuels: Coal, Oil, Natural Gas Ferrous: Iron and Steel, Cobalt, Uranium Nickel Geothermal Energy  Types of Ore Deposits Magmatic Sedimentary Rocks Pt, Cr, Fe, Ni, Ti, Diamond Fe, Cu, U, Mn, Mg Pegmatite Weathering Li, Be, U, Rare Earths, Feldspar, Mica, Secondary Enrichment: Gems Cu, Ni Hydrothermal Soils 600 C: W, Sn Al, Ni 400 C: Au, U, Ag, Co, Mo Placer 200 C: Cu, Zn, Cd, Pb Pt, Au, Sn, Ti, W, Th, Rare Earths U (Fossil), Gems Cool: Hg, As Concentration Factors and Economics Natural Abundance Geologic Processes to Concentrate Element Most involve water Intrinsic Value of Material Cost of Extraction from Earth Gold versus Gravel  Prospecting and Exploration Satellite and Aerial Photography Geochemical Sampling Remote Sensing Electrical Sounding Ground- Geological Mapping Penetrating Radar Magnetic Mapping Seismic Methods Reflection - Detailed but Gravity Mapping Expensive Radioactivity Mapping Refraction - Cheap but Not Detailed Core Sampling and Well Logging  Economic Factors in Mining Richness of Ore Quantity of Ore Cost of Initial Development Equipment, Excavation, Purchase of Rights Operating Costs: Wages, Taxes, Maintenance, Utilities, Regulation Price of the Product Will Price Go up or down?  Life Cycle of a Mine Exploration Development Active Mining Excavation Crushing, Milling, Flotation, Chemical Separation Smelting and Refining Disposal of Waste (Tailings) Shut-down  Issues in Mineral Exploitation Who Owns (Or Should Own) Minerals? Landowner, Discoverer, Government Unclaimed Areas: Sea Floor, Antarctica Who Controls Access for Exploration? Remote Sensing vs Privacy  Problems of Mining Safety Environmental Mine Wastes Problems Pollution Exploration Dust Construction and Noise Operation Sulfur (H2SO4) Economic Impact Acid Rain "Boom and Bust" Acid Runoff Cycles Dissolved Metals (Fe, Cu, Zn, As...) Soil is a Natural Resource Although many of us don't think about the ground beneath us or the soil that we walk on each day, the truth is soil is a very important resource. Think of the Earth as an egg. The shell is a very thin layer. Soil is the thin layer of the Earth’s surface. 3 Types of Soil Sand – rough, gritty, won’t form a ball Silt – smooth like flour, not sticky or shiny. Clay – soft, shiny, sticky when wet, forms ball, stains hands. When clay is heated, it hardens to make bricks and pottery. Where to Find Rocks A quarry is an open pit.  Properties of Rocks and Minerals Rocks can be classified by how they look and feel. Color, texture, and hardness are properties we look for in a rock or mineral. Color Hardness is tested by scratching a rock with your fingernail, a penny, and a nail. Texture is how much sand, silt, or clay is in the soil. Does it feel gritty, sticky, smooth, silky, moist, or dry? Rocks An aggregate of one or more minerals; or a body of undifferentiated mineral matter (e.g., obsidian); or of solid organic matter (e.g., coal) More than one crystal Volcanic glass Solidified organic matter Appearance controlled by composition and size and arrangement of aggregate grains (texture) Rock Types n Igneous n Form by solidification of molten rock (magma) n Sedimentary n Form by lithification of sediment (sand, silt, clay, shells) n Metamorphic n Form by transformations of preexisting rocks (in the solid state) Igneous Rocks Intrusive Extrusive Intrusive (plutonic) Form within the Earth Slow cooling Interlocking large crystals Example = granite Extrusive (volcanic) Form on the surface of the Earth as a result of volcanic eruption Rapid cooling Glassy and/or fine-grained texture Example = basalt Basalt: igneous extrusive Intrusive and extrusive igneous rocks Sedimentary Rocks Origin of sediment Produced by weathering and erosion or by precipitation from solution Weathering = chemical and mechanical breakdown of rocks Erosion = processes that get the weathered material moving Sediment types Clastic sediments are derived from the physical deposition of particles produced by weathering and erosion of preexisting rock. Chemical and biochemical sediments are precipitated from solution.  Clastic Chemical/biochemical Lithification The process that converts sediments into solid rock Compaction Cementation Cemented sandstone Metamorphic Rocks Regional and contact metamorphism conglomerate metaconglomerate granite gneiss The Rock Cycle The Rock Cycle Sources of Energy Nature Energy is movement or the possibility of creating movement: Exists as potential (stored) and kinetic (used) forms. Conversion of potential to kinetic. Movement states: Ordered (mechanical energy) or disordered (thermal energy). Temperature can be perceived as a level of disordered energy. Major tendency is to move from order to disorder (entropy). Importance Human activities are dependant on the usage of several forms and sources of energy. Energy demands: Increased with economic development. The world’s power consumption is about 12 trillion watts a year, with 85% of it from fossil fuels. Sources of Energy Chemical Fossil fuels (Combustion) Non-Renewable Nuclear Uranium (Fission of atoms) Chemical Energy Muscular (Oxidization) Nuclear Geothermal (Conversion) Fusion (Fusion of hydrogen) Gravity Renewable Tidal, hydraulic (Kinetic) Indirect Solar Biomass (Photosynthesis) Wind (Pressure differences) Direct Solar Photovoltaic cell (Conversion) Chemical Energy Content of some Fuels (in MJ/kg) Wood Coal Crude Oil Kerosene Ethanol Methanol Methane Natural Gas Gasoline Hydrogen 0 20 40 60 80 100 120 140 NUCLEAR ENERGY Nuclear fission uses uranium to create energy. Nuclear energy is a nonrenewable resource because once the uranium is used, it is gone! Nuclear Power Nature Fission of uranium to produce energy. The fission of 1 kg (2.2 lb) of uranium-235 releases 18.7 million kilowatt-hours as heat. Heat is used to boil water and activate steam turbines. Uranium is fairly abundant. Requires massive amounts of water for cooling the reactor. Nuclear Power Production and storage Suitable site (NIMBY) Large quantities Uranium Reactor Water Fission Waste storage and disposal Steam Turbine Electricity Nuclear Power Pro Nuclear Side Con Nuclear Side Reduced fossil fuels dependence Fear of accidents and sabotage Enhanced energy security (terrorism) Environmental benefits Waste disposal High construction and decommission costs  Nuclear fusion Currently researched but without much success. It offers unlimited potential. Not realistically going to be a viable source of energy in the foreseeable future. GEOTHERMAL Energy from Earth’s heat. Why is energy from the heat of the Earth renewable? Geothermal Energy Hydrogeothermal 2-4 miles below the earth's surface, rock temperature well above boiling point. Closely associated with tectonic activity. Fracturing the rocks, introducing cold water, and recovering the resulting hot water or steam which could power turbines and produce electricity. Areas where the natural heat of the earth’s interior is much closer to the surface and can be more readily tapped. Geothermal Energy Winter Geothermal heat pumps House Promising alternative to heating/cooling systems. Ground below the frost line 5 feet (about 5 feet) is kept around 55oF year-round. During winter: 55o F The ground is warmer than the outside. Summer Heat can be pumped from the ground to the house. House During summer: The ground is cooler than the 5 feet outside. Heat can be pumped from the house to the ground. 55o F Geothermal Energy: A Free Lunch? Environmental Problems Technical Problems of of Geothermal Energy Geothermal Energy It is Finite Corrosion Heat Sources Can Be Mineral Deposition in Exhausted (Geysers, Pipes California) Non-Productive gases (Carbon dioxide, Sulfur Emissions methane, etc.) Disposal of Mineralized Low Temperatures Brines Low Thermodynamic Efficiency  COAL, PETROLEUM, AND GAS Coal, petroleum, and natural gas are considered nonrenewable because they can not be replenished in a short period of time. These are called fossil fuels. HOW IS COAL MADE ??? Coal Nature Formed from decayed swamp plant matter that cannot decompose in the low-oxygen underwater environment. Coal was the major fuel of the early Industrial Revolution. High correlation between the location of coal resources and early industrial centers: The Midlands of Britain. Parts of Wales. Pennsylvania. Silesia (Poland). German Ruhr Valley. Three grades of coal. Coal Anthracite Carbon content (%) Highest grade; over 85% carbon. 0 20 40 60 80 100 Most efficient to burn. Lowest sulfur content; the least Energy polluting. Lignite Carbon The most exploited and most rapidly depleted. Bituminous Medium grade coal, about 50- 75% carbon content. Bituminous Higher sulfur content and is less fuel-efficient. Most abundant coal in the USA. Lignite Anthracite Lowest grade of coal, with about 40% carbon content. Low energy content. 0 500 1000 1500 2000 Most sulfurous and most polluting. Burned energy (1,000 calories per kg) Coal Coal use Thermal coal (about 90% use): Used mainly in power stations to produce high pressure steam, which then drives turbines to generate electricity. Also used to fire cement and lime kilns. Until the middle of the 20th Century used in steam engines. Metallurgical coal: Used as a source of carbon, for converting a metal ore to metal. Removing the oxygen in the ore by forcing it to combine with the carbon in the coal to form CO2. Coking coal: Specific type of metallurgical coal. Used for making iron in blast furnaces. New redevelopment of the coal industry: In view of rising energy prices. HOW ARE OIL AND GAS MADE ??? Petroleum Nature Formation of oil deposits: Decay under pressure of billions of microscopic plants in sedimentary rocks. “Oil window”; 7,000 to 15,000 feet. Created over the last 600 million years. Exploration of new sources of petroleum: Related to the geologic history of an area. Located in sedimentary basins. About 90% of all petroleum resources have been discovered. Production vs. consumption: Geographical differences. Contributed to the political problems linked with oil supply. Petroleum Use Transportation: The share of transportation has increased in the total oil consumption. Accounts for more the 55% of the oil used. In the US, this share is 70%. Limited possibility at substitution. Other uses (30%): Lubricant. Plastics. Fertilizers. Choice of an energy source: Depend on a number of utility factors. Favoring the usage of fossil fuels, notably petroleum. The Geography of Oil Is There a Lot More Undiscovered Oil? 80 per cent of oil being produced today is from fields discovered before 1973. In the 1990's oil discoveries averaged about seven billion barrels of oil a year, only one third of usage. The discovery rate of multi-billion barrel fields has been declining since the 1940's, that of giant (500- million barrel) fields since the 1960's. In 1938, fields with more than 10 million barrels made up 19% of all new discoveries, but by 1948 the proportion had dropped to only 3%. Factors of Oil Dependency Occurrence Localized large deposits (decades) Transportability Liquid that can be easily transported. Economies of scale Energy content High mass / energy released ratio Reliability Continuous supply; geopolitically unstable Storability Easily stored Flexibility Many uses (petrochemical industry; plastics) Safety Relatively safe; some risks (transport) Environment Little wastes, CO2 emissions Price Relatively low costs Oil Discovery Rates Natural Gas Reserves Substantial reserves likely to satisfy energy needs for the next 100 years. High level of concentration: 45% of the world’s reserves are in Russia and Iran. Regional concentration of gas resources is more diverse: As opposed to oil. Only 36% of the reserves are in the Middle East. Natural Gas Use Mostly used for energy generation. Previously, it was often wasted - burned off. It is now more frequently conserved and used. Considered the cleanest fossil fuel to use. The major problem is transporting natural gas, which requires pipelines. Gas turbine technology enables to use natural gas to produce electricity more cheaply than using coal. Natural Gas Liquefied natural gas (LNG) Liquid form of natural gas; easier to transport. Cryogenic process (-256oF): gas loses 610 times its volume. Value chain: Extraction Liquefaction Shipping Storage and re-gasification SOLAR Energy from the sun. Why is energy from the sun renewable? Solar Energy Definition Radiant energy emitted by the sun (photons emitted by nuclear fusion). Conversion of solar energy into electricity. Photovoltaic systems Solar thermal systems Solar Energy Level of insolation (latitude & precipitation) Sun Solar cells Mirrors Concentration Water Evaporation Conversion Steam Turbine Electricity Solar Energy Photovoltaic systems Semiconductors to convert solar radiation into electricity. Better suited for limited uses such as pumping water that do not require large amounts of electricity. Costs have declined substantially: 5 cents per kilowatt-hour. Compared to about 3 cents for coal fired electrical power. Economies of scale could then be realized in production of the necessary equipment. Japan generates about 50% of the world’s solar energy. Solar Energy Solar thermal systems Employ parabolic reflectors to focus solar radiation onto water pipes, generating steam that then power turbines. Costing about 5-10 cents per Kwh. Require ample, direct, bright sunlight. Drawback of the solar thermal systems is their dependence on direct sunshine, unlike the photovoltaic cells. Limitations Inability to utilize solar energy effectively. There is currently only about a 15% conversion rate of solar energy into electricity. Low concentration of the resource. Need a very decentralized infrastructure to capture the resource. WIND Energy from the wind. Why is energy from the wind renewable? Wind Power Potential use Growing efficiency of wind turbines. 75% of the world’s usage is in Western Europe: Provided electricity to some 28 million Europeans in 2002. Germany, Denmark (18%) and the Netherlands. New windfarms are located at sea along the coast: The wind blows harder and more steadily. Does not consume valuable land. No protests against wind parks marring the landscape. United States: The USA could generate 25% of its energy needs from wind power by installing wind farms on just 1.5% of the land. North Dakota, Kansas, and Texas have enough harnessable wind energy to meet electricity needs for the whole country. Wind Power Farms are a good place to implement wind mills: A quarter of a acre can earn about $2,000 a year in royalties from wind electricity generation. That same quarter of an acre can only generate $100 worth or corn. Farmland could simultaneously be used for agriculture and energy generation. Wind energy could be used to produce hydrogen. Limitations Extensive infrastructure and land requirements. 1980: 40 cents per kwh. 2001: 3-4 cents per kwh. Less reliable than other sources of energy. Inexhaustible energy source that can supply both electricity and fuel.  BIOMASS Energy from burning organic or living matter. Why is energy from biomass renewable? Biomass Nature Biomass energy involves the growing of crops for fuel rather than for food. Crops can be burned directly to release heat or be converted to useable fuels such methane, ethanol, or hydrogen. Has been around for many millennia. Not been used as a large-scale energy source: 14% of all energy used comes from biomass fuels. 65% of all wood harvested is burned as a fuel. 2.4 billion people rely on primitive biomass for cooking and heating. Important only in developing countries. Asia and Africa: 75% of wood fuels use. US: 5% comes from biomass sources. Biomass Biofuels Fuel derived from organic matter. Development of biomass conversion technologies: Alcohols and methane the most useful. Plant materials like starch or sugar from cane. Waste materials like plant stalks composed of cellulose. Potential and drawbacks Some 20% of our energy needs could be met by biofuels without seriously compromising food supplies. Competing with other agricultural products for land. Biomass Could contribute to reducing carbon emissions while providing a cheap source of renewable energy: Burning biofuels does create carbon emissions. The burned biomass is that which removed carbon from the atmosphere through photosynthesis. Does not represent a real increase in atmospheric carbon. Genetic engineering: Create plants that more efficiently capture solar energy. Increasing leaf size and altering leaf orientation with regard to the sun. Conversion technology research: Seeking to enhance the efficiency rate of converting biomass into energy. From the 20-25% range up to 35-45% range. Would render it more cost-competitive with traditional fuels. WATER or HYDROELECTRIC Energy from the flow of water. Why is energy of flowing water renewable? Hydropower Nature Generation of electricity using the flow of water as the energy source. Gravity as source. Requires a large reservoir of water. Considered cleaner, less polluting than fossil fuels. Tidal power Take advantage of the variations between high and low tides. Hydropower Sun Evaporation Water Sufficient and regular Precipitation precipitations Rivers Flow Reservoirs Accumulation Suitable local site Dam Gravity Turbine Power loss due to Electricity distance Hydropower Controversy Require the development of vast amounts of infrastructures: Dams. Reservoirs. Power plants and power lines. Very expensive and consume financial resources or aid resources that could be utilized for other things. Environmental problems: The dams themselves often alter the environment in the areas where they are located. Changing the nature of rivers, creating lakes that fill former valleys and canyons, etc. Water Resources Water Earth’s surface is covered by 71% water Essential for life – can survive only a few days without water Water Cycle – continuously collected, purified, recycled and distributed Flowing artesian well Precipitation Evaporation and transpiration Well requiring a pump Evaporation Confined Recharge Area Runoff Aquifer Stream Infiltration Water table Lake Infiltration Unconfined aquifer Confined aquifer Less permeable material such as clay Confirming permeable rock layer Watershed A watershed describes the total area contributing drainage to a stream or river May be applied to many scales A large watershed is made up of many small watersheds  Flowing artesian well Precipitation Evaporation and transpiration Well requiring a pump Evaporation Confined Recharge Area Runoff Aquifer Stream Infiltration Water table Lake Infiltration Zone of saturation (spaces completely filled with water) Unconfined aquifer Confined aquifer Less permeable material such as clay Confirming permeable rock layer Water sources Surface runoff – 2/3 lost to floods and not available for human use. Reliable runoff = one third Amount of runoff that we can count on year to year Groundwater Zone of saturation Water table – top of zone of saturation Aquifer – water saturated layers of sand, gravel or bedrock through which groundwater flows. Recharge slow ~ 1 meter per year Use of Water Resources Humans directly or indirectly use about 54% of reliable runoff Withdraw 34% of reliable runoff for: Agriculture – 70% Industry – 20% Domestic – 10% Leave 20% of runoff in streams for human use: transport goods, dilute pollution, sustain fisheries Could use up to 70-90% of the reliable runoff by 2025 Too Much Water: Floods Natural phenomena Aggravated by human activities Rain on snow Living on floodplains Impervious surfaces Removal of vegetation Draining wetlands Reservoir Dam Levee Flood wall Floodplain Deforestation and flooding Using Dams and Reservoirs to Supply More Water: The Trade-offs Flooded land destroys Downstream cropland and forests or cropland and estuaries are deprived of displaces people nutrient-rich silt Large losses of water through Downstream flooding evaporation is reduced Reservoir is useful for recreation and fishing Provides water for year-round irrigation of Can produce cheap electricity (hydropower) cropland Migration and spawning of some fish are disrupted Tapping Groundwater Year-round use No evaporation losses Often less expensive Potential Problems: Water table lowering – too much use Depletion – U.S. groundwater being withdrawn at 4X its replacement rate Saltwater intrusion – near coastal areas Chemical contamination Reduced stream flows  Solutions Sustainable Water Use Not depleting aquifers Preserving ecological health of aquatic systems Preserving water quality Integrated watershed management Agreements among regions and countries sharing surface water resources Outside party mediation of water disputes between nations Marketing of water rights Raising water prices Wasting less water Decreasing government subsides for supplying water Increasing government subsides for reducing water waste Slowing population growth  Pollution Source terminology Point source = pollution comes from single, fixed, often large identifiable sources smoke stacks discharge drains tanker spills Non-point source = pollution comes from dispersed sources agricultural runoff street runoff  Types of Water Pollution Sediment logging, roadbuilding, erosion Oxygen-demanding wastes human waste, storm sewers, runoff from agriculture, grazing and logging, many others Nutrient enrichment = Eutrophication N, P from fertilizers, detergents leads to increased growth in aquatic systems, ultimately more non-living organic matter  Types of Water Pollution Disease-causing organisms from untreated sewage, runoff from feed lots Toxic chemicals pesticides, fertilizers, industrial chemicals Heavy metals lead, mercury Acids (to discuss later) Elevated temperatures = Thermal Pollution water is used for cooling purposes, then heated water is returned to its original source any increase in temperature, even a few degrees, may significantly alter some aquatic ecosystems. BOD As micro-organisms decompose (through respiration) organic matter, they use up all the available oxygen. Biological Oxygen Demand (BOD) Amount of oxygen required to decay a certain amount of organic matter. If too much organic matter is added, the available oxygen supplies will be used up. Eutrophication Eutrophic – well-fed, high nutrient levels present in a lake or river Oligotrophic – poorly-fed, low nutrient levels Water bodies can be naturally eutrophic or oligotrophic, but can also be human-caused  Groundwater Pollution Agricultural products Underground storage tanks Landfills Septic tanks Surface impoundments  Oil Spills Exxon Valdez released 42 million liters of oil in Prince William Sound, contaminating 1500 km of Alaska coastline in 1989 Was the cleanup effective? Most marine oil pollution comes from non-point sources: runoff from streets improper disposal of used oil discharge of oil-contaminated ballast water from tankers Growth of population Supply & demand are in growing conflict – supply is finite – water management driven by values and needs Increases demand/use of water Increases land use and changes vegetation and permeability Increases demand for instream values – instream flows are for people The construction of dams have slowed the once flowing Columbia River into a series of lakes.